Supporting elements of this type are described in the "Tak-vaggkatalogen" ("Ceiling Wall Catalogue") issued in 1994 by Lindab AB, which shows the mounting of so-called building studs on pp 105-107 and which shows various arrangements of vertical studs and horizontal bars cooperating therewith on pp 108-109. Further examples of supporting elements in the field of the invention are shown on e.g. pp 113 and 119 in the above-mentioned catalogue. The term "supporting element" is used below as a conception of studs, sections and bars etc. for the building of walls, especially walls where building panels are mounted on supporting elements.
Furthermore Swedish Published Application SE-B457,223 (corresponding to U.S. Pat. No. 4,513,551) discloses a supporting element of U-shaped cross-section comprising a web and two side flanges for supporting building panels or the like. To facilitate the driving-in of fastening screws when mounting building panels on the supporting element (cf. the Lindab Catalogue p. 105), the side flanges have areas of so-called expanded metal which guide the fastening screws (cf. FIG. 1 in SE-B-457,223).
Such supporting elements as described above are manufactured from a flat sheet-metal blank which, in a special forming process, is formed to U-shaped cross-section. In this forming, undesired internal stress often arises in the supporting element, which may result in the entire supporting element becoming twisted, which renders the mounting operation difficult. In supporting elements of the type shown in SE-B-457,223, the expanded metal in the flanges may cause special stress which, if the worst comes to the worst, causes the free longitudinal edges of the flanges to become twisted or wave-shaped. This wave shape may arise even when the two areas of expanded metal are formed on the flat sheet-metal blank, whose longitudinal edges in unfavourable cases obtain a wave shape of such great amplitude (about 40 mm) that the handling of the strip-shaped sheet-metal blank as well as the forming into the desired supporting element are rendered difficult.
There is thus a need of a new supporting element which tends to a less extent to be twisted and which does not have the above-mentioned undesired wave shape.
A further general desire, which is well known to the expert, is that the supporting element should have good rigidity and withstand the linear loads perpendicular to the flanges, which arise during mounting and also when subjecting the finished wall to loads. Various measures have been suggested for the reinforcing of supporting elements, and examples are shown on p. 113 in the Lindab catalogue mentioned by way of introduction, in which the web of the supporting stud has been provided with two parallel longitudinal reinforcements in the form of grooves.
However, the market now requires still more rigid supporting elements, which is the starting point of this invention. There is a need of a new type of supporting element, which has improved strength and rigidity and whose flanges in particular are reinforced such that they yield towards each other to a smaller extent when subjected to loads, for instance when mounting building panels thereon.
As a further example of prior art, mention can be made of the supporting element according to U.S. Pat. No. 4,619,098, which for the purpose of reducing the heat and cold conductivity is formed with slits. The above-described inconvenience, i.e. undesired internal stress and insufficient rigidity, however, is not discussed in this reference.